1. Field of the Invention
The present invention relates to an imaging field frame switching apparatus that switches imaging fields such as those for the viewfinders of cameras.
2. Related Background Art
In a previously submitted Japanese Patent Application Laid-Open No. 6-18979, the present applicant made a proposal concerning a camera that can switch photo-taking aspect ratios. The aspect ratio for a full size imaging field (the vertical and the lateral ratio of an imaging field) is 1:1.8 and is represented by "H", the aspect ratio for a vertical trimming imaging field is about 1:1.5 and is represented by "L", and the aspect ratio for a lateral trimming imaging field is about 1:2.8 and is represented by "P".
FIGS. 27 through 29 are diagrams for an example where two different light interception states for an imaging field are selected by using a photoelectric device, such as a liquid crystal device, and an imaging field size display, which is disclosed in Japanese Patent Application Laid-Open No. 6-18979, is provided for a viewfinder.
FIG. 27 is a diagram showing all the masking patterns that are employed for a liquid crystal device. Reference number 201 denotes a view frame of a full size imaging field "H"; 202a, 202b, 202c, and 202d, common liquid crystal mask patterns; 203a and 203b, vertical liquid crystal mask patterns; 204a and 204b, lateral liquid crystal mask patterns. Discontinuous regions are present between the patterns at their divisions, as is shown in FIG. 27.
FIG. 28 shows the display state of a vertically elongated imaging field "L", with the common liquid crystal mask patterns 202a, 202b, 202c, and 202d and the vertical liquid crystal mask patterns 203a and 203b in the light intercepted state. FIG. 29 shows the display state of the laterally elongated imaging field "P", with the common liquid crystal mask patterns 202a, 202b, 202c, and 202d and the lateral liquid crystal mask patterns 204a and 204b in the light intercepted state. The full size imaging field "H" is displayed by setting all the liquid crystal mask patterns to a transparent state.
In the above described conventional example, however, since there are gaps between the common liquid crystal mask patterns 202 and the vertical liquid crystal mask patterns 203, and between the common liquid crystal mask patterns 202 and the lateral liquid crystal mask patterns 204, discontinuous portions appear when the imaging fields "L" and "P" are displayed, and unwanted light transparent portions exist, causing an imaging field to have a strange and unnatural appearance.
In Japanese Utility Model Publication No. 2-34670 has been proposed a technique which is performed within a viewfinder by employing a photoelectric device, such as a liquid crystal device. FIGS. 30A though 30D show the switching of imaging field sizes and the display of a selected imaging field, which is disclosed in the above Utility Model Publication. There are first display patterns (A.sub.1 and A.sub.2), where an imaging field size is represented by linear patterns, and second display patterns (B.sub.1 and B.sub.2), which are employed to intercept light that is outside the first display patterns. An imaging field size can be changed by a first mode (in FIGS. 30B and 30D), where the first and second display patterns are employed to set the external region along the imaging field to an almost complete light intercepted state, and by a second mode (in FIGS. 30A and 30C), where only the first display pattern is employed to represent only the frame of the imaging field by linear patterns and to set the external, full size imaging field region to its fully transparent state.
In the above described conventional case, however, when the second mode is selected to enable the viewing of an image in the external region of the first display pattern, an image that is in an external region of a predetermined imaging field presents as good a target as an image that is in the predetermined imaging field, and a photographer might take a picture while erroneously considering the entire visible field to be a photographic image field, regardless of the presence of an imaging field frame. In addition, as there are many pattern separation lines, the discontinuous portions due to the pattern divisions are noticeable and disconcerting when the first mode is displayed. This is not desirable and makes a photographer feel insecure.